gno.land/p/jeronimoalbi/pager/v0⧉

1// Package pager provides pagination functionality through a generic pager implementation.2//3// Example usage:4//5//	import (6//	    "strconv"7//	    "strings"8//9//	    "gno.land/p/jeronimoalbi/pager/v0"10//	)11//12//	func Render(path string) string {13//	    // Define the items to paginate14//	    items := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}15//16//	    // Create a pager that paginates 4 items at a time17//	    p, err := pager.New(path, len(items), pager.WithPageSize(4))18//	    if err != nil {19//	        panic(err)20//	    }21//22//	    // Render items for the current page23//	    var output strings.Builder24//	    p.Iterate(func(i int) bool {25//	        output.WriteString("- " + strconv.Itoa(items[i]) + "\n")26//	        return false27//	    })28//29//	    // Render page picker30//	    if p.HasPages() {31//	        output.WriteString("\n" + pager.Picker(p))32//	    }33//34//	    return output.String()35//	}36package pager3738import (39	"errors"40	"math"41	"net/url"42	"strconv"43	"strings"44)4546var ErrInvalidPageNumber = errors.New("invalid page number")4748// PagerIterFn defines a callback to iterate page items.49type PagerIterFn func(index int) (stop bool)5051// New creates a new pager.52func New(rawURL string, totalItems int, options ...PagerOption) (Pager, error) {53	u, err := url.Parse(rawURL)54	if err != nil {55		return Pager{}, err56	}5758	p := Pager{59		query:          u.RawQuery,60		pageQueryParam: DefaultPageQueryParam,61		pageSize:       DefaultPageSize,62		page:           1,63		totalItems:     totalItems,64	}65	for _, apply := range options {66		apply(&p)67	}6869	p.pageCount = int(math.Ceil(float64(p.totalItems) / float64(p.pageSize)))7071	rawPage := u.Query().Get(p.pageQueryParam)72	if rawPage != "" {73		p.page, _ = strconv.Atoi(rawPage)74		if p.page == 0 || p.page > p.pageCount {75			return Pager{}, ErrInvalidPageNumber76		}77	}7879	return p, nil80}8182// MustNew creates a new pager or panics if there is an error.83func MustNew(rawURL string, totalItems int, options ...PagerOption) Pager {84	p, err := New(rawURL, totalItems, options...)85	if err != nil {86		panic(err)87	}88	return p89}9091// Pager allows paging items.92type Pager struct {93	query, pageQueryParam                 string94	pageSize, page, pageCount, totalItems int95}9697// TotalItems returns the total number of items to paginate.98func (p Pager) TotalItems() int {99	return p.totalItems100}101102// PageSize returns the size of each page.103func (p Pager) PageSize() int {104	return p.pageSize105}106107// Page returns the current page number.108func (p Pager) Page() int {109	return p.page110}111112// PageCount returns the number pages.113func (p Pager) PageCount() int {114	return p.pageCount115}116117// Offset returns the index of the first page item.118func (p Pager) Offset() int {119	return (p.page - 1) * p.pageSize120}121122// HasPages checks if pager has more than one page.123func (p Pager) HasPages() bool {124	return p.pageCount > 1125}126127// GetPageURI returns the URI for a page.128// An empty string is returned when page doesn't exist.129func (p Pager) GetPageURI(page int) string {130	if page < 1 || page > p.PageCount() {131		return ""132	}133134	values, _ := url.ParseQuery(p.query)135	values.Set(p.pageQueryParam, strconv.Itoa(page))136	return "?" + values.Encode()137}138139// PrevPageURI returns the URI path to the previous page.140// An empty string is returned when current page is the first page.141func (p Pager) PrevPageURI() string {142	if p.page == 1 || !p.HasPages() {143		return ""144	}145	return p.GetPageURI(p.page - 1)146}147148// NextPageURI returns the URI path to the next page.149// An empty string is returned when current page is the last page.150func (p Pager) NextPageURI() string {151	if p.page == p.pageCount {152		// Current page is the last page153		return ""154	}155	return p.GetPageURI(p.page + 1)156}157158// Iterate allows iterating page items.159func (p Pager) Iterate(fn PagerIterFn) bool {160	if p.totalItems == 0 {161		return true162	}163164	start := p.Offset()165	end := start + p.PageSize()166	if end > p.totalItems {167		end = p.totalItems168	}169170	for i := start; i < end; i++ {171		if fn(i) {172			return true173		}174	}175	return false176}177178// TODO: Support different types of pickers (ex. with clickable page numbers)179180// Picker returns a string with the pager as Markdown.181// An empty string is returned when the pager has no pages.182func Picker(p Pager) string {183	if !p.HasPages() {184		return ""185	}186187	var out strings.Builder188189	if s := p.PrevPageURI(); s != "" {190		out.WriteString("[«](" + s + ") | ")191	} else {192		out.WriteString("\\- | ")193	}194195	out.WriteString("page " + strconv.Itoa(p.Page()) + " of " + strconv.Itoa(p.PageCount()))196197	if s := p.NextPageURI(); s != "" {198		out.WriteString(" | [»](" + s + ")")199	} else {200		out.WriteString(" | \\-")201	}202203	return out.String()204}205